DH was optional (default on), which still lets launchers/exporters skip
it and left the server's LOD data unused. Drop the [option] block so it
is required and installed for every client.
The server generates and serves DH LODs, but DH was opted out by default,
so clients never received them. Default it on (still optional/opt-out) so
players get server-side distant terrain out of the box.
Adds an [option] block so Distant Horizons is a user-toggleable mod instead
of always installed, matching how Controlify is already declared.
default = false expresses opt-in wherever the consuming exporter supports
it: modrinth/export.go reads only Optional, so in an mrpack the mod becomes
a toggle (that format has no off-by-default concept), while
curseforge/export.go reads Default and marks it optional-and-disabled.
Nothing in the pack depends on or conflicts with Distant Horizons, so no
other mod is left unsatisfied by it being skippable.